In his math class, William took 4 exams. His scores were 77, 91, 82, and 78. What was his average score on the exams?
The average is the sum of his scores divided by the number of scores. There are 4 scores and their sum is $77 + 91 + 82 + 78 = 328$ His average score is $328 \div 4 = 82$.